The present invention relates to foundry molds and the like and to compositions and methods for treating and manufacturing such foundry products. More particularly, the present invention relates to improved foundry molds and to novel coatings, impregnates and binding compositions, and methods of treating and preparing foundry molds, investment molds, furnace and ladle refractories, ceramic cores and like foundry products to enhance their high-temperature strength and refractoriness.
Various forms of silicate-containing compositions such as those disclosed in U.S. Pat. Nos. 4,113,499; 4,111,705; 3,961,968; 3,957,715; 3,682,668; 3,576,652; 3,211,560; and 2,842,445, are known for treating foundry molds and other such products. These silicate-containing compositions are incorporated either as a binder of the refractory material used in making the mold or as an impregnate or coating of the mold made from such material. Commonly, other ingredients are included with the silicate-containing composition to produce a treating mixture generally effective for its intended purpose. Some prior art compositions have been directed to the manufacture of air-setting or no-bake molds to eliminate the need for heat curing. However, these prior art compositions frequently produce air-setting molds having skins or treated surfaces of insufficient strength to withstand molten metal conditions encountered in foundry operations. For example, molds treated with prior art compositions do not always provide skins effective to withstand the intense heat and erosion due to agitation of the hot, turbulent metal which is poured into the mold cavity. Other treating compositions have produced skin structures prone to cracking when highly heated. Still others permit undesirable metal penetration into the sand of the mold, adverse chemical reactions, and spalling of the cavity surface.
Accordingly, a primary object of the present invention is to provide new and improved foundry products having superior treated surfaces for resisting intense heat, erosion, metal penetration and spalling when exposed to turbulent hot metal during foundry operations.
Another object of the present invention is to provide new and improved compositions for treating foundry molds and like products to enhance their strength and refractoriness.
Another object of the present invention is to provide new and improved foundry mold treating compositions which can be used either as mold coatings, as binders for the mold material, or as impregnates to enhance bond strength and refractoriness of treated mold surfaces.
Another object of the present invention is to provide mold coating compositions and methods of making molds which produce coatings on the surfaces of mold cavities of substantial thickness and of high bond strength and refractoriness.
Other objects, features, and advantages of the present invention will become apparent from the subsequent description and the appended drawing in which the sole FIGURE is a vertical cross section, with parts broken away, of a typical casting mold utilizing the improvements constituting the invention.